A pressure vessel requires a closure system which can withstand the pressure differential between the interior of the vessel during use and the external, atmospheric pressure. Such a pressure vessel may be employed as a cleaning vessel in a dry cleaning machine. For cleaning vessel applications, it is preferable to provide a door which does not pose the risk of contaminating the materials to be passed therethrough with foreign substances associated with the door. Specifically, in the dry cleaning machine context, it is important that lubricants necessary for the proper operation of the door not come into contact with the garments or other materials loaded into the machine. Such materials may be referred to generically as substrates.
In the prior art, the risk of lubricant contamination arises due to the provision of a rotatable lock ring, having greased lugs, mounted on the high-pressure cleaning vessel. When a door is swung open, the substrates to be cleaned or those already cleaned must be moved through an opening defined by the greased lock ring.
A further disadvantage associated with closures for prior art pressure vessels is that having the rotatable lock ring proximate the vessel results in a deeper entrance path into the interior of the pressure vessel. When the lock ring is disposed on the face of a dry cleaning machine, it adds significantly to the length of the entrance tunnel into the cleaning vessel. Consequently, it is difficult for an operator to reach into the pressure vessel to remove the substrates; in so doing, the operator's own clothing may be contaminated by the greased lock ring.
It would therefore be desirable to have a closure system for a pressure vessel such as a cleaning vessel of a dry cleaning machine which does not provide a risk of contamination to substrates passing through the closure system, and which offers a relatively short entrance tunnel into the associated cleaning vessel.